Preparation method of self-powered graphene / SiC heterojunction ultraviolet photoelectric detector

Abstract

The invention relates to a preparation method of a self-energized graphene / SiC heterojunction ultraviolet photoelectric detector, which comprises the following steps of: firstly, preparing a silicon carbide pyrolytic graphene sample on a silicon carbide carbon surface, then, obtaining a partially protected photoresist protection layer with an interdigitated structure on the graphene surface, and then, carrying out oxygen plasma treatment to obtain a graphene / SiC heterojunction ultraviolet photoelectric detector. The oxygen plasma treatment regulates and controls the electronic structure of the epitaxial graphene of the SiC part, through the oxygen plasma treatment, the part of graphene generates vacancy defects, the Fermi level of the graphene is reduced, the work function of the graphene is improved, and the doping type of the graphene is gradually converted into a p type. According to the preparation method provided by the invention, a heterojunction with good quality is formed between the SiC substrate and the epitaxial graphene, a heterojunction with good quality is formed between the defective graphene and the non-defective graphene, a self-energized system is successfully constructed under the action of a built-in electric field, and the self-energized graphene / SiC heterojunction ultraviolet photoelectric detector is successfully obtained.

Description

Technical Field

[0001] The invention relates to a method for preparing a self-powered graphene / SiC heterojunction ultraviolet photoelectric detector, and belongs to the field of semiconductor devices. Background Art

[0002] With the continuous development and progress of modern production and life technology, the design requirements for sensor systems in different application scenarios are becoming higher and higher, such as space exploration, monitoring of toxic or harmful conditions on submarines or warships. With the continuous development of sensor systems, their structures have become more and more complex, and the number of internal detectors has increased, which undoubtedly poses a huge challenge to the energy supply of the entire sensor system. At present, most traditional detectors use batteries to maintain the operation of the entire system. When the number of detectors increases, the battery-powered mode increases the structural complexity of the entire system, resulting in an increase in the size and weight of the sensor system. In addition, traditional sensor systems require staff to regularly maintain and replace batteries. For sensor equipment set in dangerous and extreme environments, this not only increases the operating cost of the system, but also poses a threat to the life safety of staff. These problems will bring great difficulties to the further development of sensor systems. The emergence of self-powered detectors and related research enable devices to continue to work without external power, which greatly reduces the complexity of the entire system design and provides a possibility for solving the above problems.

[0003] The self-powered technology in semiconductor photodetection devices is mainly based on the photovoltaic effect, pyroelectric effect, etc., most of which are achieved by constructing PN junctions or Schottky junctions. However, it is difficult to achieve high-quality p-type doping in most semiconductors, so most of the reported self-powered UV photodetectors basically use vertical Schottky junctions to construct the self-powered system. However, these Schottky junction photodetectors inevitably require high-quality Schottky contacts on the semiconductor surface, which also increases the difficulty and cost of device preparation. Therefore, how to achieve a simple and reliable self-powered system in UV photodetectors is of great research significance.

[0004] As a two-dimensional material with excellent performance, graphene can not only be used to construct photodetectors, but also capture and store energy. Therefore, it plays an important role in various self-powered sensing systems, such as acting as a flexible electrode and forming a Schottky junction with semiconductor materials. Silicon carbide (SiC), as a third-generation wide-bandgap semiconductor material, has the characteristics of large bandgap width, high critical breakdown electric field strength, fast carrier saturation migration velocity, and high thermal conductivity. Due to different atomic arrangements, SiC has a large number of allotropes, among which 4H-SiC has greater advantages in the preparation of ultraviolet photodetectors. For SiC epitaxial graphene, its naturally formed graphene / SiC heterojunction interface can avoid the heterostructure construction process in the preparation of ultraviolet photodetectors, thereby making it easier to build a self-powered system, greatly reducing the production cost of the device and the required process complexity.

[0005] For SiC carbon surface (000-1) epitaxial multilayer graphene, it does not have a transition layer structure, so there is basically no interaction between graphene and SiC substrate, showing the characteristics of random orientation, forming a disordered rotational stacking arrangement. This disordered rotational stacking arrangement leads to weak interaction between graphene / SiC layers, making it exhibit electrical properties similar to single-layer graphene, that is, its dispersion relation near the κ point shows a linear Dirac cone structure similar to single-layer graphene, so it has a higher carrier mobility. This makes carbon-surface graphene / SiC more promising in the preparation of high-frequency power electronic devices.

[0006] Patent document CN108231953B (CN201711482215.1) discloses an MSM structure 4H-SiC ultraviolet photodetector with a graphene transparent electrode. It epitaxially grows a semi-insulating layer on an n-type 4H-SiC substrate, cuts the sample into rectangular strips, grows a Si-surface multilayer graphene film by an electrolytic thermal method, and prepares an ultraviolet photodetector with an MSM structure by photolithography patterning and ICP etching process. The multilayer graphene film on the Si surface of the detector cannot form a heterojunction, so it has no self-powered and position response characteristics. Patent document CN113707757A (202110779389.4) discloses a method for regulating the light response performance of an ultraviolet photodetector. The method uses photoresist as a protective layer to regulate the aspect ratio of the graphene strips on the surface of the sample through an oxygen plasma treatment process, thereby improving the detector light response speed and responsiveness. However, the detector does not construct a heterojunction between graphenes of different structures, and does not have self-powered and position-responsive characteristics.

[0007] So far, self-powered technology for graphene / SiC ultraviolet photodetectors has not been reported. Therefore, there is an urgent need for a simple and efficient method for preparing epitaxial graphene / SiC heterojunction ultraviolet photodetectors with self-powered characteristics. Summary of the invention

[0008] In view of the deficiencies in the prior art, the present invention provides a method for preparing a self-powered graphene / SiC heterojunction ultraviolet photodetector.

[0009] The ultraviolet photoelectric detector prepared by the invention not only has self-power supply, but also has the light spot position response characteristic.

[0010] Explanation of terms

[0011] PN junction: Through processes such as epitaxy, dopant diffusion or ion implantation, P-type semiconductor and N-type semiconductor are produced on the same semiconductor substrate. The boundary or interface between these two semiconductor materials is called a PN junction.

[0012] Bandgap width: Bandgap width refers to the width of a band gap (in electron volts (ev)). The energy of electrons in solids cannot be continuous, but rather a number of discontinuous energy bands. To conduct electricity, there must be free electrons or holes. The energy band where free electrons exist is called the conduction band, and the energy band where free holes exist is called the valence band. In order for bound electrons to become free electrons or holes, they must obtain enough energy to jump from the valence band to the conduction band. The minimum value of this energy is the bandgap width.

[0013] Heterojunction: The interface region formed by the contact of two different semiconductors. According to the different conductivity types of the two materials, heterojunctions can be divided into homogeneous heterojunctions and heterogeneous heterojunctions. Usually, the conditions for the formation of heterojunctions are: the two semiconductors have similar crystal structures, similar atomic spacing and thermal expansion coefficients.

[0014] The present invention is achieved through the following technical solutions:

[0015] A method for preparing a self-powered graphene / SiC heterojunction ultraviolet photodetector comprises the following steps:

[0016] 1) Preparing silicon carbide pyrolytic graphene samples by pyrolysis method;

[0017] 2) cleaning and drying the silicon carbide pyrolytic graphene sample obtained in step 1); performing photoresist, exposure, and development, and obtaining a partially protected photoresist protective layer of an interdigitated structure on the graphene surface by a photolithography process;

[0018] 3) treating the sample obtained in step 2) with oxygen plasma, and then cleaning and drying the sample to obtain an interdigitated structure in which defective graphene regions and non-defective graphene regions intersect each other;

[0019] 4) The sample obtained in step 3) is subjected to a photolithography process and an electron beam deposition process to deposit a uniform layer of metal on the surface of the sample, and then cleaned and dried to obtain a self-powered graphene / SiC heterojunction ultraviolet photodetector.

[0020] Preferably according to the present invention, in step 1), graphene is pyrolyzed on the carbon surface of silicon carbide, the graphene is 3-10 layers of graphene, and the silicon carbide is semi-insulating 4H-SiC.

[0021] Preferably according to the present invention, in step 1), the pyrolysis method is carried out according to the existing method for preparing graphene.

[0022] Preferably according to the present invention, in step 1), the size of the silicon carbide pyrolytic graphene sample is 10 mm*10 mm, the thickness is 350 μm, the surface off-axis angle is 0 degree, and the error is within 0.3 degree.

[0023] Preferably according to the present invention, in step 2), the partially protected interdigitated finger-like structure includes a first comb-like structure and a second comb-like structure, the first comb-like structure and the second comb-like structure form an interdigitated finger-like structure, there is no gap between the first comb tooth and two adjacent second comb teeth, wherein the first comb-like structure or the second comb-like structure is protected by a protective layer.

[0024] Preferably according to the present invention, in step 2), the width of the teeth of the first comb-like structure and the second comb-like structure is 0.5-5 mm.

[0025] Further preferably, in step 2), the width of the teeth of the first comb-like structure and the second comb-like structure is 0.63 mm.

[0026] Preferably according to the present invention, in step 2), the photolithography process is performed according to the prior art in the art.

[0027] Preferably according to the present invention, in step 3), the oxygen gas flow rate of the oxygen plasma treatment is 300-600 ml / min, the working power is 280w, and the treatment time is 1-5min.

[0028] Further preferably, in step 3), the oxygen gas flow rate of the oxygen plasma treatment is 450-500 ml / min, the working power is 280 w, and the treatment time is 2-3 min.

[0029] The partially protected photoresist protective layer of the interdigitated finger-like structure is treated with oxygen plasma. The oxygen plasma treatment regulates the electronic structure of the SiC epitaxial graphene. The unprotected interdigitated finger-like structure graphene produces vacancy defects, which lowers the Fermi level of graphene, increases its work function, and gradually transforms its doping type to p-type. In this way, a SiC-graphene heterojunction is formed between the SiC substrate and the epitaxial graphene, and a graphene-graphene heterojunction is formed between the defective graphene and the non-defective graphene. Under the action of the built-in electric field, a self-energy system is successfully constructed.

[0030] Preferably according to the present invention, in step 4), the photolithography process and the electron beam deposition process are performed according to the prior art in the art, and the photoresist area is symmetrically distributed in the shape of long strips.

[0031] All equipment and raw materials in the method of the present invention are commercially available products.

[0032] The technical features and excellent effects of the present invention are:

[0033] 1. The present invention first prepares a silicon carbide pyrolytic graphene sample on the carbon surface of silicon carbide, then obtains a partially protected photoresist protective layer with an interdigitated structure on the graphene surface, and then performs oxygen plasma treatment. The oxygen plasma treatment regulates the electronic structure of the SiC partially epitaxial graphene. Through the oxygen plasma treatment, vacancy defects are generated in part of the graphene, which reduces the Fermi level of the graphene, improves its work function, and gradually transforms its doping type into p-type.

[0034] 2. The preparation method of the present invention forms a good quality heterojunction between the SiC substrate and the epitaxial graphene, and a good quality heterojunction between the defective graphene and the non-defective graphene. Under the action of the built-in electric field, a self-powered system is successfully constructed, and a self-powered graphene / SiC heterojunction ultraviolet photodetector is successfully obtained.

[0035] 3. Use optical power density of 176.8mW / cm 2 The self-powered graphene / SiC heterojunction ultraviolet photodetector prepared without external bias was tested for light response under 365nm ultraviolet light. In the two response modes of voltage and current, the self-powered graphene / SiC heterojunction ultraviolet photodetector has stable and fast response characteristics, and this type of detector also has a spot position response characteristic.

[0036] 4. The self-powered graphene / SiC heterojunction ultraviolet photodetector prepared by the method of the present invention has relatively simple equipment and process, and has excellent effects, further increasing the application value of related devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The schematic diagram of the structure of the self-powered graphene / SiC heterojunction ultraviolet photodetector prepared by the method of the present invention.

[0038] In the figure: 01, semi-insulating 4H-SiC substrate, 02, defective graphene, 03, non-defective graphene, 04, metal electrode.

[0039] Figure 2 Schematic diagram of the spot position response test of the self-powered graphene / SiC heterojunction ultraviolet photodetector prepared by the method of the present invention under ultraviolet light irradiation.

[0040] Figure 3 The voltage and current cycle response test results of the self-powered graphene / SiC heterojunction ultraviolet photodetector prepared by the method of the present invention under ultraviolet light irradiation without external bias are as follows:

[0041] In the figure: a, b, c are the voltage cyclic response test results; d, e, f are the current cyclic response test results; the cyclic response test results of the device when the light spot is located on the right side of the photodetector surface (a), (d), the cyclic response test results of the device when the light spot is located in the middle of the photodetector surface (b), (e), and the cyclic response test results of the device when the light spot is located on the left side of the photodetector surface (c), (f). DETAILED DESCRIPTION

[0042] The preparation method of a self-powered graphene / SiC heterojunction ultraviolet photodetector of the present invention is further described below in conjunction with the embodiments and drawings, but is not limited thereto.

[0043] The embodiment uses a semi-insulating 4H-SiC substrate sheet combined with graphene, which has a size of 10mm*10mm, a thickness of about 350μm, a surface off-axis angle of 0 degree, and an error within 0.3 degrees. It is provided by the Institute of New Generation Semiconductor Materials of Shandong University.

[0044] The photoresponse performance test of the photodetector uses an independently built test platform. The excitation light sources used include laser diodes in various visible light bands and an LED UV lamp with a fixed output power of 200W and a wavelength of 365nm. The source meter involved in the test is KEYSIGHT B2902A. The maximum output voltage is 210V, and the minimum measurement resolution is 1fA / 100nV.

[0045] Embodiment 1:

[0046] A method for preparing a self-powered graphene / SiC heterojunction ultraviolet photodetector, the steps are as follows:

[0047] 1) preparing a semi-insulating 4H-SiC carbon surface 5-layer pyrolytic graphene by pyrolysis method, soaking it in acetone and ethanol for 10 minutes and ultrasonic cleaning it to obtain a cleaned sample;

[0048] 2) the sample obtained in step 1) is subjected to photoresist, exposure, and development, and a photoresist protective layer of a partially protected interdigitated finger-like structure is obtained on the graphene surface by a photolithography process, wherein the partially protected interdigitated finger-like structure includes a first comb-like structure and a second comb-like structure, wherein the first comb-like structure and the second comb-like structure form an interdigitated finger-like structure, wherein there is no gap between the first comb teeth and two adjacent second comb teeth, wherein the first comb-like structure or the second comb structure is protected by the protective layer, and the comb teeth width of the first comb structure and the second comb structure is 0.63 mm;

[0049] 3) treating the sample obtained in step 2) with oxygen plasma, with an oxygen gas flow rate of 400 ml / min, a working power of 280 w, and a treatment time of 1 min, to obtain an interdigitated structure in which defective graphene regions and non-defective graphene regions intersect;

[0050] 4) Soaking the sample obtained in step 3) in acetone and ethanol for 10 minutes and then ultrasonically cleaning;

[0051] 5) subjecting the sample obtained in step 4) to photoresist, exposure, and development, and obtaining a photoresist protective layer with a long strip-shaped symmetrical distribution structure on the graphene surface by using a photolithography process;

[0052] 6) subjecting the sample obtained in step 5) to an electron beam deposition process to deposit a uniform layer of metal on the surface of the sample;

[0053] 7) Soak the sample obtained in step 6) in acetone and ethanol for 10 minutes to clean it, and obtain two symmetrical strip metal electrodes to complete the preparation. The structure of the obtained self-powered graphene / SiC heterojunction ultraviolet photodetector is as follows: Figure 1 shown.

[0054] Embodiment 2:

[0055] A method for preparing a self-powered graphene / SiC heterojunction ultraviolet photodetector, the steps are as follows:

[0056] 1) preparing semi-insulating 4H-SiC carbon-surface multilayer pyrolytic graphene by pyrolysis method, soaking it in acetone and ethanol for 10 minutes and ultrasonic cleaning it to obtain a cleaned sample;

[0057] 2) the sample obtained in step 1) is subjected to photoresist, exposure, and development, and a partially protected photoresist protective layer of an interdigitated finger-like structure is obtained on the graphene surface by a photolithography process, wherein the partially protected interdigitated finger-like structure includes a first comb-like structure and a second comb-like structure, wherein the first comb-like structure and the second comb-like structure form an interdigitated finger-like structure, wherein there is no gap between a first comb tooth and two adjacent second comb teeth, wherein the first comb-like structure or the second comb structure is protected by the protective layer, and the comb tooth width of the first comb structure and the second comb structure is 1.25 mm;

[0058] 3) treating the sample obtained in step 2) with oxygen plasma, with an oxygen gas flow rate of 450 ml / min, a working power of 280 w, and a treatment time of 2 min, to obtain an interdigitated structure in which defective graphene regions and non-defective graphene regions intersect;

[0059] 4) Soaking the sample obtained in step 3) in acetone and ethanol for 10 minutes and then ultrasonically cleaning;

[0060] 5) subjecting the sample obtained in step 4) to photoresist, exposure, and development, and obtaining a photoresist protective layer with a long strip-shaped symmetrical distribution structure on the graphene surface by using a photolithography process;

[0061] 6) subjecting the sample obtained in step 5) to an electron beam deposition process to deposit a uniform layer of metal on the surface of the sample;

[0062] 7) The sample obtained in step 6) is soaked in acetone and ethanol for 10 minutes for cleaning to obtain two symmetrical strip metal electrodes, thus completing the preparation.

[0063] Embodiment 3:

[0064] A method for preparing a self-powered graphene / SiC heterojunction ultraviolet photodetector comprises the following steps:

[0065] 1) Prepare semi-insulating 4H-SiC carbon surface multilayer pyrolytic graphene by pyrolysis method, soak it in acetone and ethanol for 10 minutes and ultrasonically clean it to obtain a cleaned sample;

[0066] 2) the sample obtained in step 1) is subjected to photoresist, exposure, and development, and a photoresist protective layer of a partially protected interdigitated finger-like structure is obtained on the graphene surface by a photolithography process, wherein the partially protected interdigitated finger-like structure includes a first comb-like structure and a second comb-like structure, wherein the first comb-like structure and the second comb-like structure form an interdigitated finger-like structure, wherein there is no gap between the first comb teeth and two adjacent second comb teeth, wherein the first comb-like structure or the second comb structure is protected by the protective layer, and the comb teeth width of the first comb-like structure and the second comb-like structure is 2.5 mm;

[0067] 3) treating the sample obtained in step 2) with oxygen plasma, with an oxygen gas flow rate of 450 ml / min, a working power of 280 w, and a treatment time of 2 min, to obtain an interdigitated structure in which defective graphene regions and non-defective graphene regions intersect;

[0068] 4) Soaking the sample obtained in step 3) in acetone and ethanol for 10 minutes and then ultrasonically cleaning;

[0069] 5) subjecting the sample obtained in step 4) to photoresist, exposure, and development, and obtaining a photoresist protective layer with a long strip-shaped symmetrical distribution structure on the graphene surface by using a photolithography process;

[0070] 6) subjecting the sample obtained in step 5) to an electron beam deposition process to deposit a uniform layer of metal on the surface of the sample;

[0071] 7) The sample obtained in step 6) is soaked in acetone and ethanol for 10 minutes for cleaning to obtain two symmetrical strip metal electrodes, thus completing the preparation.

[0072] Embodiment 4:

[0073] A method for preparing a self-powered graphene / SiC heterojunction ultraviolet photodetector, the steps are as follows:

[0074] 1) Prepare semi-insulating 4H-SiC carbon surface multilayer pyrolytic graphene by pyrolysis method, soak it in acetone and ethanol for 10 minutes and ultrasonically clean it to obtain a cleaned sample;

[0075] 2) the sample obtained in step 1) is subjected to photoresist, exposure, and development, and a photoresist protective layer of a partially protected interdigitated finger-like structure is obtained on the graphene surface by a photolithography process, wherein the partially protected interdigitated finger-like structure includes a first comb-like structure and a second comb-like structure, wherein the first comb-like structure and the second comb-like structure form an interdigitated finger-like structure, wherein there is no gap between the first comb teeth and two adjacent second comb teeth, wherein the first comb-like structure or the second comb structure is protected by the protective layer, and the comb teeth width of the first comb structure and the second comb structure is 5 mm;

[0076] 3) treating the sample obtained in step 2) with oxygen plasma, with an oxygen gas flow rate of 500 ml / min, a working power of 280 w, and a treatment time of 3 min, to obtain an interdigitated structure in which defective graphene regions and non-defective graphene regions intersect;

[0077] 4) Soaking the sample obtained in step 3) in acetone and ethanol for 10 minutes and then ultrasonically cleaning;

[0078] 5) subjecting the sample obtained in step 4) to photoresist, exposure, and development, and obtaining a photoresist protective layer with a long strip-shaped symmetrical distribution structure on the graphene surface by using a photolithography process;

[0079] 6) subjecting the sample obtained in step 5) to an electron beam deposition process to deposit a uniform layer of metal on the surface of the sample;

[0080] 7) The sample obtained in step 6) is soaked in acetone and ethanol for 10 minutes for cleaning to obtain two symmetrical strip metal electrodes, thus completing the preparation.

[0081] Experimental example:

[0082] 1. The self-powered graphene / SiC heterojunction ultraviolet photodetector prepared in Example 1 has an optical power density of 176.8 mW / cm 2 The spot position response test results are shown in the 365nm ultraviolet light irradiation. Figure 2 As shown, through Figure 2 It can be seen that the obtained detector has a spot position response characteristic.

[0083] 2. Use optical power density of 176.8mW / cm 2The detector prepared in Example 1 was tested for light response under 365 nm ultraviolet light without external bias. Figure 3 It can be seen that in the two response modes of voltage and current, the self-powered graphene / SiC heterojunction ultraviolet photodetector prepared in Example 1 has stable and fast response characteristics, and this type of detector also has a spot position response characteristic. In the process of testing the light response of the device, when the device is irradiated with ultraviolet light, if the spot position is located on the right side of the device surface, the potential difference between the two electrodes of the device decreases, and the source-drain current shows a negative gain (such as Figure 3 (a), (d)); if the UV spot is located in the middle of the device surface, the potential difference between the two electrodes of the device still decreases, and the source-drain current still shows a negative gain, but its reduction is less than the reduction in the potential difference when the spot is located on the right side (as shown in Figure 3 (b), (e)); if the UV spot is located on the left side of the device surface, the potential difference between the two electrodes of the device increases, and the source-drain current shows a positive gain (as shown in Figure 3 (c), (f)).

Claims

1. A method for preparing a self-powered graphene / SiC heterojunction ultraviolet photodetector, comprising the following steps: 1) Preparing silicon carbide pyrolytic graphene samples by pyrolysis method; 2) washing and drying the silicon carbide pyrolytic graphene sample obtained in step 1); Performing photoresist, exposure, and development, and using a photolithography process to obtain a partially protected photoresist protective layer of an interdigitated finger-shaped structure on the graphene surface; 3) treating the sample obtained in step 2) with oxygen plasma, and then cleaning and drying the sample to obtain defective graphene and non-defective graphene regions with interdigitated structures; 4) The sample obtained in step 3) is subjected to a photolithography process and an electron beam deposition process to deposit a uniform layer of metal on the surface of the sample, and then cleaned and dried to obtain a self-powered graphene / SiC heterojunction ultraviolet photodetector.

2. The preparation method according to claim 1, characterized in that: In step 1), graphene is pyrolyzed on the carbon surface of silicon carbide, the graphene is 3-10 layers of graphene, and the silicon carbide is semi-insulating 4H-SiC.

3. The preparation method according to claim 1, characterized in that: In step 1), the pyrolysis method is carried out according to the existing method for preparing graphene.

4. The preparation method according to claim 1, characterized in that: In step 1), the size of the silicon carbide pyrolytic graphene sample is 10 mm*10 mm, the thickness is 350 μm, the surface off-axis angle is 0 degree, and the error is within 0.3 degree.

5. The preparation method according to claim 1, characterized in that: In step 2), the partially protected interdigitated finger-like structure includes a first comb-like structure and a second comb-like structure, the first comb-like structure and the second comb-like structure form an interdigitated finger-like structure, there is no gap between the first comb tooth and two adjacent second comb teeth, wherein the first comb-like structure or the second comb-like structure is protected by a protective layer.

6. The preparation method according to claim 1, characterized in that: In step 2), the width of the teeth of the first comb-like structure and the second comb-like structure is 0.5-5 mm.

7. The preparation method according to claim 1, characterized in that: In step 3), the oxygen gas flow rate of oxygen plasma treatment is 300-600 ml / min, the working power is 280w, and the treatment time is 1-5min.

8. The preparation method according to claim 1, characterized in that: In step 3), the oxygen gas flow rate of oxygen plasma treatment is 450-500 ml / min, the working power is 280w, and the treatment time is 2-3min.

9. The preparation method according to claim 1, characterized in that: In step 4), the photolithography process and the electron beam deposition process are performed according to the prior art in the art, and the photoresist area is symmetrically distributed in the shape of long strips.

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